Dude, are you sure you kicked him out? 'Cause it sounds like you're giving him another shot next week.

It should go something like this:

Hey man, to be perfectly blunt and not beat around the bush, you're just not working out with us. We have a very good idea of what we should sound like and you're just not where we need you to be, musically.

And he would ask, "wha...what??? What-do-ya-mean?????"

And then you need to be brutally honest:

"Dude, we think you SUCK!!!!!" Now, quit wasting our time, if you wanna hang out, help us carry our gear to gigs and maybe do beer runs for us during practice that's cool but you can't hold a note in a bucket and you certainly can't carry our band anymore"

That's just an example of how it's done so that there's no question of your intent. Probably how i would handle the sitch.

That seems a little harsh. Funny, but harsh. You can help us carry our gear and do beer runs? Are you for real?

I had to fire a guitar player about a month ago. Not because he isn't a good player but because he was a jerk and made being in a band not fun. I just asked him if he had respect for the other guys in the band because he sure didn't act like it. In the end, I told him to shape up or ship out. He ended up shipping out. He offered to stick with us for a little while longer to cover some dates but I told him we already had a guy on standby. That felt good.